The typical mattress has a tufted surface with shallow indentations. To provide greater comfort and support for the body, and to protect the mattress itself, a pad is often placed between the mattress and the sheets. Such pads are traditionally composed of down, especially in feather beds, which provide great cushioning, loft and insulation, but which are excessively warm for many sleepers, and are relatively difficult to clean. Other commonly used pads are composed of cotton wadding, quilted within fabric layers. This material is easily laundered, but provides little loft or cushioning. Sheepskin, which is also used, provides cushioning, loft and insulation like down, but is often an allergen and is difficult to clean. Desirable filling material for mattress padding should be lightweight, resilient and washable. It should be soft to provide comfort, but not so delicate that it compresses completely under the weight of the reclining body. It is also helpful if the pad retains its shape and position on the mattress to allow sleeping comfort in any position.
Natural materials such as down, cotton wadding or batting, kapok and the like have been widely used in the past for mattress padding but are now being replaced by synthetic materials, such as spun polyester fiber, and Dacron. Flexible foam material, such as convoluted foam padding, in some forms referred to as "egg crate" material, has many advantages, but lacks luxuriousness and smoothness. The very popular polyester fiber filling is disadvantageous because it tends to flatten out after time in use. The use of polyurethane foam is advantageous in several respects. The contour of the foam can be shaped to conform to the body; the foam is generally nonallergenic; it is easily cleaned; and it is relatively durable.
It has become recognized, however, that air circulation between the body and the foam product is necessary for the user's comfort. Various attempts have been made to enhance circulation, and one of the most common expedients is to form the surface of the foam abutting the body into corrugations or convolutions. These may take the form of repetitive series of peaks and valleys. However, when the head or body of a user rests on such a surface, it is in direct contact with a plurality of points which tend to bend or be crushed. The body is not contacted as desired by a smooth surface, but rather by separated pressure points which may improve air circulation but which may still give rise to discomfort. Also, of course, the feeling of cushioned resilience which is normally associated with such foam products is not had.